Protagonist' refers to -

• Protagonist:
- Central character or leading character of a play.
- নাটকের কেন্দ্রীয় চরিত্র। 

• In other words:
- The leading character, hero, or heroine of a drama or other literary work.
- A proponent for or advocate of a political cause, social program, etc.
- The leader or principal person in a movement, cause, etc.

Source: lecture & Cambridge Dictionary grammar reference.